1. Field of the Invention
The present invention relates to fluorescent lamps and, more particularly, to a device for replacing a rapid-start or instant start type fluorescent lamp in a fixture in which these lamps are serially connected.
2. Description of the Prior Art
Fluorescent lamps of the rapid-start or instant start type, hereinafter simply referred to as lamps, are extensively used for illumination (lighting), particularly in commercial establishments, such as office building and industrial facilities. Most fixtures for such lamps are designed to accommodate an even number of lamps, typically two or four. In the rapid start type fixture a separate transformer, often referred to as a ballast, is included for each pair of lamps which when inserted in the fixture become connected in series with a winding of the transformer. In a two-lamp fixture a single transformer is included, while two such transformers are included in a four-lamp fixture. In an instant start type fixture a transformer with an auxiliary winding is also used for each pair of lamps with the secondary winding connecting two lamps in series. The failure or removal of one lamp deactivates the other lamp with which it is connected in series. Thus, in a two-lamp fixture if one lamp fails, generally being referred to as burned out, or is removed the other lamp is deactivated and therefore no illumination is produced.
The recent energy crisis in the United States has greatly affected the life of most Americans. In localitites where electrical power is generated by the use of fossil type fuel, the curtailment of the use of electrical power by about 20% in private homes as well as in commercial and industrial establishments was requested or ordered by law. In order to comply with these requests many lamps had to be removed from existing fixtures. In a two-lamp fixture, the removal of one lamp deactivated the other, and therefore the area or space which the already installed two-lamp fixture was to illuminate was darkened. In a four-lamp fixture the removal of one lamp deactivated one of the remaining lamps, so that illumination was provided by only two of the remaining three lamps, resulting in an illumination reduction of 50%. The removal of the lamps resulted in unsatisfactory light distribution, since, in constructing the buildings, the fixtures were located to provide proper lighting with all lamps in operation.
While the unsatisfactory light distributon was expected, in order to reduce power consumption the actual reduction in power was not as great as hoped for, due to the particular manner in which the conventional transformer used for each pair of lamps is connected to the power lines. Such a transformer hereinafter also referred to as a two-lamp transformer, in the case of the rapid start fixture, has a portion of its main or primary winding permanently connected across the power lines. In the case of the instant start fixture, the primary winding is connected permanently across the power lines. This is clearly seen in IES Lighting Handbook, Fourth Edition, published in 1966 by the Illuminating Engineering Society, 345 East 47th Street, New York, N.Y. 10017, on pages 8-24, FIGS. 8-33d. The shown schematic diagram is typical of practically all the transformers (or ballasts) used for rapid-start lamps. Consequently, some current flows in the portion of the main or primary winding across the lines and power is consumed even when no illumination is produced, either due to the absence of both lamps or the absence of one lamp which results in the deactivation of the other lamp. Thus, the mere removal of a lamp without disconnecting the transformer from the power lines does not result in total power saving.
In addition, in the absence of one or both lamps the power drawn by the transformer is very inductive. In an institution such as a scientific research institution, in which various pieces of equipment are operated, a requirement is often placed on the institution by the power department to adjust the power factor of all consumed power to a value of one. This is generally achieved by power-factor adjustment equipment, typically in the form of a large rotary capacitor which is very expensive. In such an institution, the added inductive loading of transformers by fixtures, from which lamps were removed, complicates the power factor adjustment. Thus, the removal of lamps from fixtures, in addition to resulting in disadvantageous light distribution does not produce the desired power saving proportional to the reduction in the illumination, and furthermore, adversely affects the power factor of the consumed power.